Anchored earth retaining walls or "bulkheads" are a typical method of supporting earth and dividing land from water to create wharf age.
Bulkhead designs vary, but in general consist of a wall member constructed of materials such as wood, metal, or concrete driven or inserted into the ground. At times, the bulkhead stands alone and does not need any additional buttressing. For example, in marine applications, where the water is fairly shallow and the wall fairly short, driving the bottom edge of the wall to a sufficient depth below the ground surface provides enough support for the wall that it is able to function without reinforcement. However, frequently, it is necessary to provide support for the wall additional to that resulting from the wall's implantation in the ground, such as (referring now to the preceding example) when the water is deep or the wall is high.
The usual method of providing additional support utilizes a tie rod connected at one of its ends to the wall, and at its other end to a deadman or "ground anchor". An alternative technique is to secure one end of one or more tie rods to the bulkhead wall and fix the other end of each tie rod in the ground. The tie rods are oriented such that they slope downwardly from the location of attachment to the bulkhead wall to the location of fixation in the ground.
In typical conventional configurations, the bulkhead is supported laterally by a wale and a tie back system which transmits the lateral earth load from the wall to a deadman located at some distance behind the face of the bulkhead.
All bulkhead walls undergo deterioration over time. This is especially the case with steel sheet pile walls. Additionally, there can be numerous other reasons for replacing, repairing, modifying, or reinforcing such walls.
Wall replacement is not a desirable option because it entails partial or complete demolition of the existing wall and disruption of traffic and other functions in the general area behind the existing wall during installation of the replacement wall. Nevertheless, comprehensive rebuilding of bulkheads is often necessary when deterioration of the wall member is substantial.
In lieu of comprehensive rebuilding, the usual "fix" has consisted of driving sheeting outboard of the existing sheeting, excavating inland of the original steel wall, and installing new tie rods attached to the new sheeting. To secure the new sheeting or wall with tie rods, the ground inland of the original wall must be removed. The tie rods must then be attached to the new wall and/or to an anchor located at a relatively large distance from the wall. This is followed by backfilling inland of the original steel wall, and filling the space between the new sheeting and old wall.
The repair technique described in the preceding paragraph is both time consuming and expensive. Since the tie rod and deadman are installed prior to backfilling, the expensive technique of working from a barge or trestle may be required. A further disadvantage is that backfilling over and around a tendon or tie rod may result in flexure and tensioning of the tie rod, thereby increasing the chance of tie rod failure. Another disadvantage is that temporary support of the new bulkhead during testing of the tie rods is usually required. And, it is a major shortcoming that this technique does not utilize the existing bulkhead, including the functional tie back/wale system.
U.S. Pat. No. 4,728,225 to Brandl et al. discloses a bulkhead rehabilitation method akin to the foregoing technique, wherein new tie rods are installed in addition to new sheeting.
Another bulkhead rehabilitation technique is disclosed in U.S. Pat. No. 4,480,945 to Schnabel. New tie rods are installed, running from the original bulkhead under rehabilitation to a location inboard of the bulkhead, with accompanying expense and difficulty. A sufficient number of tie rods are installed so that all additional required support is provided by the new tie rods. The technique disclosed in the '945 patent does not appear to make use of a new bulkhead wall.
The art would be advanced by provision of an alternative to the foregoing which is more conveniently and efficiently implemented.